The present invention disclosed herein relates to an optical receiver and a method of forming the same, and more particularly, to an optical receiver including an optical detector and a hetero-junction bipolar transistor and a method of forming the same.
A photo detector is a device that uses an internal photoelectric effect, i.e., a method in which an injected photon makes an electron and a hole that are free charge carriers in a semiconductor. For example, such a device includes a p-n junction photodiode, a positive intrinsic negative (PIN) photodiode, and an avalanche photodiode.
An optical receiver mainly used in a laser radar system may have a structure in which the PIN photodiode and a hetero-junction bipolar transistor are integrated. However, the photo detector of the optical receiver does not easily adjust an electric field applied to an In(0.53)Ga(0.47)As layer in which a band gap for absorbing light is very narrow. Thus, since a leakage current is generated by a tunneling effect, the applied the electric field is limited in density. In addition, since an amount of the light incident onto a surface of the photo detector is limited, the light missing the surface of the photo detector is lost, thereby decreasing external quantum efficiency.
Since the PIN photodiode does not generally have a gain when an optical signal is electrically converted, it is difficult to manufacture an optical receiver in which a photo detector having superior receive sensitivity is integrated.